Vivesh Vir Kapur

Globally, the fossil record of the co-occurrence of alpheids (mainly claw fingertips) and gobiids (mainly otoliths) is a rarity. Herein, we record a diverse assemblage (comprising a total of nine species) of alpheid shrimps (based on fossilised claw fingertips) assigned to the genus Alpheus (including a new species: Alpheus indicus sp. nov.) from the early Miocene (Burdigalian) Quilon Formation, Kerala Basin, southwest India. These alpheid remains co-occur with fossil remains (mainly otoliths) of numerous gobiid fish genera, including Medoborichthys (represented by M. podolicus ) within the Quilon Formation. This fossil evidence supports the idea that the mutualistic relationship(s) within these groups had developed before the Burdigalian. Based on the geographic distribution of alpheids and gobiids fossils, it is evident that these groups quite likely thrived persistently in a mutualistic relationship(s) within the shallow coasts of the Paratethys Sea and the Indian Ocean realms during the Neogene (Aquitanian to Burdigalian). Further, older (Paleogene) records from the subcontinent are certainly warranted to provide support to any argument in favour of the enhancement of a complex snapping claw within alpheids and/or the development of the mutualistic relationship(s) between alpheids and gobiids during the early Paleogene (early Eocene) within India.

The past two decades have witnessed a renewed interest in the Neogene (mainly Miocene) interval of the Kachchh (= Kutch) region owing to its potential to yield numerous records on fishes, reptiles, birds, and marine and terrestrial mammals. However, the Piscean (mainly selachian) faunal records from the Neogene (Miocene) interval have been sparsely emphasized. The current investigation reveals the most diverse assemblage of selachian (shark) fauna, to date, from the Aquitanian (~ 21 Ma) Khari Nadi Formation at Kotada, Kutch Basin, western India. The recovered selachian (shark) fauna comprises five genera, including Galeocerdo, Physogaleus, Carcharhinus, Negaprion and Hemipristis representing seven species. The presence of Galeocerdo mayumbensis, Carcharhinus falsiformis, and C. brevirostris comprise the oldest Neogene records from the Kutch Basin, western India. The diversity similarity coefficient data suggests that the Aquitanian selachian assemblage is quite dissimilar compared to the previously known Langhian-Serravallian assemblage from the Kutch Basin, western India. Global distribution of the selachian fauna reveals intermittent biogeographic connectivity between the Atlantic, the Mediterranean, and the Indian Oceanic realms during the Aquitanian to Tortonian. However, complete stratigraphic records across various Oceanic realms are warranted to fully understand the diversity change(s) and the direction(s) of migration(s) of the selachian fauna. Considering the data on Modern relatives of the recovered selachian fauna, it is most likely that the recorded selachian fauna dwelled in warm-temperate to tropical shallow coastal waters in the Neritic to Intertidal zones, i.e., coastal-reef to mesopelagic environment(s).